Manufacture of decolorizing carbon and the like



Patented Oct. 18, 1932 ROBERT N. RIDDLE, OF PHILADELPHIA, PENNSYLVANIA,ASSIGNOB, '10 RIDDLE P300388 OOIPANY, O1 PHILADELPHIA,

NEW YORK PENNSYLVANIA, A CORPORATION 01? IANUI'ACTURE OF DECOLORIZINGCARBON AND THE LIKE Io Drawing.

M invention relates to the manufacture of ecolorizing carbon and thelike, being concerned with the production of a form of carbon(hereinafter referred to as activated carbon) that has valuabledecolorizing, clarifying, and deodorizing properties, and is also usefulfor various other purposes. The invention affords an expeditious,convenient, and economical method or process of manufacture. 7

In producing my carbon from forms of carbon such as coal, I employanother material of the character hereinafter indicated, with which Iassociate the particles of coal in a pulverized state of fine division,in such wise that the coal particles are invested, coated or embedded inthe other material. I heat the thus prepared fine coal sufliciently toliberate much or all of its volatile matter, and even subject it to asuflicient tem perature to cause some combustion of its residual fixedcarbon, on exposure to the air,- all, however, without permitting freeand total combustion and consumption of the fixed carbon, and withoutsintering or coking together the original fine carbonaceous particles,such sintering or coalescence, (as well as free or rapid combustion ofthe coal) being prevented by the presence or action of the othermaterial. After the heating operations are completed, the carbon productmay be freed of the other material or its residue.

As the other material in my process as above outlined, I may make use ofa substance such as sodium carbonate, which is soluble, so that it canbe brought into intimate relations with the coal particles by solutionand evaporation; affords the coal particles an investure sufiicientlyrefractory not to burn away, fuse, or coalesce at the temperaturesrequired in my process to distil away those 1 hydrocarbons which mightfuse and cement the carbonaceous Earticles together; does not chemicallyalter t e fixed carbon of the coal;

- and is inexpensive. But many other materials are known which possesssimilar pro erties in greater or less degree, and may used for thepurposes of my invention: especially the various alkali metal salts andcompounds, and the alkali metal carbonates Application fled February 24,1980. Serial No. 431,051.

in particular,though I believe that few such substances are so cheap assodium carbonate. V

In associating the sodium carbonate or the like with the coal bysolution and evaporation, I find it of great advantage to make use'of awetting agent for the coal,-i. e., some reagent that will cause bettercontact of the water with the coal, like a fatty acid or some substancecontaining or yielding a fatty acid, and particularly a fatty acid ofthe open chain series. Water-soluble soa is a fatty acid reagent of thissort; and may also instance stearates and commercial fats of variouskinds. I have found that the use of such a wetting agent greatlyabbreviates the time required to complete the preparatory treatment ofthe coal with the so dium carbonate, and produces variousotherbeneficial effects.

In particular, the use of such an agent tends toward better contact ofthe ultimately deposited soda with the coal; makes the dried mass ofcoal and soda break up easily into a. soft and perfect powder; andresults in a smooth escape of the gases when the powder is heated. 1also believe that during the heating the fatty acid slowly decomposesand produces beneficial catalytic or other effects, particularly asregardsthe decomposition of the saturated and unsaturated components ofthe coal: i. e., it results in a larger proportion of gaseous and liquidproducts. For exemple, a soft gas coal having fixed carbon may yieldcarbon when treated as hereinafter described. Apparently this additionalcarbon (resulting from decomposition of the volatile constituents of thecoal) considerably improves the absorptive power of the final productfor gums, albumenoids, pectins, allurones, etc., and gives the productthe power of concurrently filtering, clarifying and purifying.

Commercial soft coal of any good quahty 'may be used, but I prefer thekind known as high volatile, and particularly gas coking coal: e. g.Pittsburgh gas coal with 40% volatiles, or Westmoreland coal of similarcharacter. This should be pulverized to a fineness of about 200 mesh (orfiner) as for Parts Beef tallow 100 Caustic soda (NaOH) 30 Water--- 60 Asmall addition of aqueous ammonia greatly facilitates the mixing, but isnot essential: if it is used, an amount whose ammonia (NIL) content is10% of the rest of the mixture will give ood results. Or a correspondingamount 0 ammonium carbonate may be used. This keeps the mass mealy whensubsequently heated.

The amount of the soap used should be about 1% of the amount of coal, bywelght. The sodium carbonate used should be about 30-40% of the coal,also by weight.

The soap having been prepare the SOdlllIIl carbonate, in 15% aqueoussolution, is stirred andmixed in with the soap. This ma be done at atemperature of about 80 C. 1s mixture is placed in a steam 1acketedkettle also e uip ed with agitators or scrapers, an then the riedpulverized coal is added and thoroughly mixed in without stirring, at atemperature of about 100 C.

After the coal has been stirred in, the temperature is gradually raised,and the liquid mass is kept boiling until all the water has been driedout,be1ng vigorously stirred all the while. The mass tends to frothduring the heating, but does not stick together permanently.

An alternative mode of treatment is to keep the mass at the boilingpoint for about an hour, checking the evaporation by careful regulationof the heat, and then heating vigorously and drying out all the water.The mass will first become sticky and then break up into a fine, soft,velvety powder.

In either case, if the product is not a fine, loose powder, faultystirring is indicated; then the mass should be screened through aISO-mesh sieve.

The carbon product. in the form of a dry, loose powder, is put in aretort previously heated to a low red (about 300-400 C.) and is broughtup to some 500-600 C.,--or even to 700 C.,-and held at the final heatfor a period that depends on the temperature: i. e., for 500 0.,three'hours may be required; for 600 (1., two hours may suffice; whilefor and then freed of the residue of the sodium carbonate by washing ashereinafter described. I

If it is to be further treated, however, it

may be taken out of the retort (with being allowed to cool appreciably)into a pan with a cover that can readily be raised and lowered to limitand control the access of air and the supply of oxygen. By raising andlowering the cover, the carbon is kept ust glowing,- being stirredvigorously all the time. This is continued till ammonia ceases to comeoff, when the cover is closed down on the pan and the material allowedto cool.

A test of the proper completion of this glowing operation is to heat u aportion of the material to substantially t e temperature at which theglowing was carried out, If no ammonia comes off when this is done, theprocess can be considered properly completed.

After cooling, the residue of the sodium carbonate can be removed fromthe product and recovered by washing the product with water, decantingor filterin off the solution, treatin the resldue with ilute acid (e.hydroc loric or sulphuric acid), and was ing it again with water. About8090% of the original sodium carbonate can be recovered from the firstwash water.

The carbon produced by this glowing step is equal to the best in thetrade 1n decolorizing power, and is unique in its clarifying anddecolorizing capacity, and especially in its power to absorb' ectins,gums, albumenoids, etc. The yie d of carbon is about -55% of theoriginal coal by weight.

The yield from the retorting operation, if cooled and washed withoutglowing, is about -70% of the original coal; but the ualit is only abouthalf as good as after t e g owing. Apparently the glowing operationpurifies the decolorizing carbon by eliminating carbon of little or nodecolorizing power. I

The recovery of soda on washing is greater after the glowing operationthan without the glowing.

As an alternative to heat treatment in a retort and in a pan as abovedescribed, the dried mixture may be treated in an externally heatedrevolving drum, without access of air, but with provisions for ventingit of the gases arising from the o eration. Heating under theseconditions Wlll require about an hour, at a low red heat (about 600 to700 (3.). After this, the material may be taken out and either lowed ina. pan as before, or assed throug a revolving drum externally eated toabout 500 to 700 C., steam bein concurrently passed into or, through therum. Under these conditions, the steam is decomposed and its oxygenreacts with the carbon or carbonaceous material of the coal; but theexothermic action is less pronounced or striking than in the open pantreatment, and the operation is slower.

Having thus described my invention, I claim 1. A process of preparingfinely divided clarifying and decolorizing carbon, which processcomprises forming a mixture of pulverized coal with a solution of analkali metal salt and water soluble soap; boiling ofi the ,A

water and thereby investing the coal particles with a deposit ofmaterial from the solution; heatin the thus prepared coal to atemperature of redness, with exclusion of air and avoidance of fusionand sintering together of the carbonaceous particles; and then treatingthe latter at a glowing heat with a limited supply of oxidizing agentuntil ammonia has ceased to come off.

2. A process for preparing clarifyin and decolorizing carbon, whichcomprises eating pulverized coal having its particles invested withrefractory material to a temperature of redness, with exclusion of airand avoidance of fusion and sintering together of the carbonaceousparticles, and then treating the latter at a glowing heat with a limitedsupply of oxidizing agent until ammonia has ceased to come 3. A processfor preparing clarifyin and decolorizin carbon, which comprises eatingpulverized coal having its particles invested with an alkali metal saltto a temperature of redness, with exclusion of air and avoidance offusion and sintering together decolorizing carbon, which processcomprises formin a mixture of pulverized coal with a solution of analkali metal compound, together with a fatty acid reagent, and boilingof! thewater. p

In testimony v whereof, I have hereunto signed my name at Philadelphia,Pennsylvania, thls 19th day of February, 1930. ROBERT N. RIDDLE.

